[SOLVED]Formula producing wrong result

Hi all! I could really use your help with this.

So, here are columns A, B, and C. I was supposed to copy the data from column B to column C and change the labels to "Optimal Price".

Next, formula =B7*(1+B4*(1-C8/B8)) was entered to cell C7. I didn't come up with this formula myself, but got it from the textbook instructions for this assignment.

The value in cell C7 is definitely supposed to be 10,486 when $12.97 is entered into C8. Again, got both numbers from the instructions.

But it is not. What is wrong? All the other formulas copied from column B are identical in column C. I haven't changed anything in column B or C, except for entering the formula in C7 and the new unit price in C8.

How would it even be possible to get that value (10,486)? I calculated the answer manually, and the answer is 10,490 (rounded).

What have I done wrong?

Edit: Added the workbook